Magnetic curl breaker



March 3,1970 D. N. QBENsHAlN 3,498,873

' MAGNETIC cum. BREAKER Filed May 29,1968 4 sheets-sheet-x March 3, 1970D. Nr.7oBENsHAlN yMAGNETIC CURL `BREAKER 4 Sheets-Sheet 2.

Filed llay 29, 1968 w m /l n@ M 2 w, @l mi qw 4\ G W. y.

ma lay 29. .1968-, 4 sheets-snm s y INVENT OR David Nae/ Obensha/'n 1..la7C-Alam..

ATTORNEY March 3, 1970 D. N. OBENSHAIN MAGNETIc cum. BREAKER mea may 29,1968 4 Sheets-Sheet 4 INVENTOR David iNoel Obenshain ATTORNEY Liu-10.

United States Patent O 3,498,878 MAGNETIC CURL BREAKER David NoelObenshain, Luke, Md., assignor to Westvaco Corporation, a corporation ofDelaware Filed May 29, 1968, Ser. No. 733,001 Int. Cl. D21h 1/00 U.S.Cl. 162-271 13 Claims ABSTRACT OF THE DISCLOSURE An apparatus ispresented for decurling a we'b of paper or the like which includes arotatable rod cradled throughout its length on anti-friction bearingsand held in position -by a plurality of spaced apart magnetic devices.

BRIEF SUMMARY OF INVENTION When paper is manufactured, the finishedpaper is generally wound on cores for shipment to the customer, or forprocessing into sheets, or other converted paper products. The cores arerelatively small, ranging from around two inches to eight inches inoutside diameter. A very popular size is a three inch core which has anoutside diameter of three and one-half inches.

Due to the fact that the paper is wrapped onto the core under tensionthroughout its length, and to the relatively long time that the rollsare stored, the paper tends to partially conform to the curvatureestablished by the core. When unwound, the paper is thus found to haveacquired a permanent curvature or, as referred to in the industry, thepaper contains cur In the outer portions of the rolls the curl may bevery minor, if it can be detected at all. However, as the paper isunwound down to the core, the curl becomes more and more pronounced. Inmany instances, the curl is so great that the paper cannot be used forits intended purpose. Sometimes, as much as to 15 percent of the paperin a roll has to be discarded due to so called roll curl. Even beforethe point is reached on a roll of paper where the paper has to -bediscarded, the curl present may require slowing down of a sheetingmachine to avoid jamups in the sheet transporting and stackingmechanisms.

Curl breakers or decurlers of various types have been used to reduce thelosses of paper as a result of excess roll curl. Conventional decurlersmade from a sharp-edged bar are suitable in some instances with the mostelfective being a 'bar with a small radius edge around which the paperweb is caused to travel. The side of the paper web opposite from thecurl -bears against the edge to induce a reverse curl, therebycounteracting the roll curl. By properly adjusting the angle of bendaround such bars, the roll curl can be quite easily removed and, in someinstances, the paper can |be made to curl in the opposite direction ifdesired. Such bars, however, are not suitable for use on highly finishedor coated paper, since the edge of the bar tends to scratch the coatedsurface of the paper. The same decurling problem would be encounteredwith coated paperboard which suffers from the same mechanical curlproblems when stored in roll form.

In addition, decurlers having a round cross-section in the form ofcylindrical rolls have been proposed to eliminate the scratchingproblem, but these devices did not prove satisfactory for other reasons.Namely, because the rolls were made too large in diameter, the decurlingoperation could not be effectively performed. Smaller diameter rollswere then tried, but because of their tendency to deiiect when supportedonly at the ends, they too did not eifectively decurl the web. It asfound that to properly decurl a web of easily scratched paper, the rollshad tol be in the order of one-half inch diameter or smaller rice and aweb width in the order of 12 to 18 inches was the maximum that could lberun. Attempts were then made to cradle decurling rolls, or rods, of agreater width at intermediate points throughout their lengths bymeans ofball Ibearings or other low friction elements. At nominal web speeds of1000 feet per minute, a one-half inch diameter rod would have to rotateat 7,650 rpm. It was found that at speeds well below the above rate, thesmall diameter rod would tend to whip and ride-up out of the supports.

To solve this latter problem the present invention was conceived. It wasfound that a small diameter rod rotating at high speed could be retainedin the cradle formed by low friction support means by arranging beneaththe rod and close to, but not touching same, a plurality of permarientmagnets or the like located between spaced support means. With thepresent arrangement, web speeds up to 2000 feet per minute have beenattained with-no tendency for the rotating rod to whip and ride-up outof its supports. The ultimate speed limit is not yet known.

It is accordingly an object of the present invention to provide arotatable rod decurling means which effectively acts to decurl atensioned web and overcomes the above mentioned difiiculties andshortcomings of conventional decurlers.

It is another object of the present invention to provide a smalldiameter rotatable decurling rod having means for preventing theintermediate deilection thereof.

Still another object of the present invention is to provide a fullysupported small diameter rotatable decurling rod capable of high speedoperation with means to prevent it from whipping and riding up IOut ofits supports.

More particularly, the present invention provides a small diameter,rotatable decurling rod, of any desired length with intermediatelow-friction support means spaced throughout its length, and with novelmagnetic means, close to 'but not touching the decurling rod, to retainit in its supports at high rotational speeds.

DESCRIPTION OF THE DRAWING FIGURE l shows a front elevation of a curlbreaker assembly, broken at its center;

FIGURE 2 shows a frontal detail of one unit of the curl breakerassembly;

FIGURE 3 shows a sectional view taken at lines 3-3 of FIGURE 2;

FIGURE 4 shows a sectional view taken at lines 4-4 of FIGURE 2;

FIGURE 5 shows a plan view of a curl breaker assembly partially insection;

FIGURE 6 shows a cross sectional view of a dual curl breakerinstallation and its supporting means;

FIGURE 7 shows a frontal detail of a modied curl breaker unit;

FIGURE 8 shows a sectional View taken at lines 8 8 of FIGURE 7;

FIGURE 9 shows a sectionalview taken at lines 9-9 of FIGURE 7;

FIGURE 10 shows a curl -breaker rod with a plastic covering;

FIGURE 11 shows an end view of the plastic covered rod of FIGURE 10;

FIGURE 12 shows another modiiied curl breaker rod formed from a helicalspring;

FIGURE 13 shows schematically how the curl breaker rod installation ofthe invention could be used as a bowed roll; and,

FIGURE 14 is a sectional view taken at lines 14-14 of FIGURE 13 to showone form of mounting for the bowed roll.

3 DETAILED DESCRIPTION sheeting, inspecting, sorting and stacking paperfinishing machine, the magnetic decurler of the present invention hasshown a substantial decrease in the paper loss due to roll curl. Theapparatus was installed on the machine as an eXtra attachment andwithout altering the previous design of the machine. The onlyrequirements for a suitable installation being one which allows the webto be tensioned when passed over the decurler bar, and one which allowsSome degree of movement to vary the angle of wrap around the decurlerbar. Experiments illustrated that with a relatively small diameter rod(one-half inch in diameter) the amount of curl removed or inducedincreased steadily up to about 60 degrees wrap around the rod. Beyondthat point there was only slight increase in curl removal. Also, it wasfound that a given angle of wrap removed or induced more curl as thebasis weight of the web increased.

Referring to the drawing, and particularly to FIGURE 1, the apparatus ofthe present invention is illustrated as being mounted on a rigid supportmeans 10. The support means 10 may be in turn mounted on movable armswhereby the angle of wrap of the web around the rod can be changed, orit may be xed in place in a location which permits the web angle of wrapto be changed by movable guide means before and/or after the Web passesover the rod. Additionally, the rigid support means 10 must be locatedsuch that the web is tensioned when it passes over the rod, andpreferably in a place that permits easy access and operator convenience.FIGURE 6 of the drawing shows one example of how the curl breaker of thepresent invention might be located as a part of a paper finishingapparatus. There is a dual installation 4depicted n FIGURE 6 wherein tworigid support bars 10 are shown installed on arm assembly 2 which is inturn pivotally mounted on shaft 7 supported by machine frame member 4. Asimilar arm assembly and frame at the opposite side of the machine wouldsupport the opposite ends of bars 10. This arrangement is used tocontrol both up and down curl sometimes found in a single paper roll. Asillustrated, the curl breaker assemblies are mounted between a pair ofrolls 5, 6 on the machine in a place where the web W is under tension.The position of one of the curl breaker assemblies 2 in contact with thepaper web W is shown in broken lines. A single installation could besimilarly arranged as a part of a paper finishing apparatus.

Referring again to FIGURE l, there is illustrated a side view of atypical curl breaker assembly. The structural support for the assemblycomprises the rigid bar member 10 of'rectangular cross section as shownin FIG- URES 3 and 4. The bar member 10 does not necessairly have to berectangular in cross section, as long as it is rigid enough to preventexcessive deflection. The top of the bar has machined therein a grooveor slot 16 to insure accurate alignment of the bearing support blocks 12and the magnets 26. Thebearing support blocks 12 are attached tothe barby means of screws 14, FIGURE 4. The magnets are likewise attached bymeans of screws 28, FIGURE 3.

FIGURE 2 is an enlarged view of the right end of the assembly of FIGURE1, showing the curl breaker rod 30, end thrust bearing 32, end block 33,bearing support blocks 12, bearing shafts 20, bearing spacers 18 and 19,`bearings 2.2, 24 and magnet 26. The curl breaker rod 30 is preferablymade of case hardened and ground tool steel having a Rockwell C hardnessof around 60. It may be chrome plated if desired. Other materials may beused as long as they are magnetically attractive. Each end of the rod ismachined and has lightly pressed thereon a thrust bearing 32. End block33 is rigidly attached to the rigid support bar 10 by screws 35, seeFIGURE 5. Each end block 33 has recessed in the face thereof an opening34 to receive the bearing 32 with approximately 1/16 inch clearance inall directions. This clearance allows the rod to position itself freelyon supporting bearings 22, 24 and to have end float to provide forthermal expansion of the rod. Recessing the bearing into the end block33 is a safety precaution to prevent accidental loss of the rod in casesome abnormal condition momentarily knocks thel rod out of the cradleformed by the bearings 22, 24. Bearing blocks 33 are of course mountedat each end of the rod 30 as shown in FIGURE 1.

Referring now to FIGURE 5, the bearing support blocks 12 each haveopenings machined therein for receiving lbearing shafts 20. A bearingand spacer sleeves 18 and 19 are mounted on each shaft 20. The sleevesare of different lengths and are arranged as shown so that the twobearings 22, 24 supported by a pair of mounting blocks are in staggeredor offset relation with each other with an overlapping relationship asthey form a cradle for supporting the rod. That is, for each pair ofbearings 22, 24, their respective axes of rotation are spaced apart adistance less than the diameter of one ball bearing. By arranging thebearings in this manner, the rod 30 is positioned more or less on top ofthe bearing surfaces which allows a greater angle of wrap of the web tobe achieved than would be allowed if the rod 30 were cradled in a deeperV-shaped space formed by opposed ball bearings. It should also bepointed out that the bearings 22, 24 could 'be mounted on opposite sidesof a single bearing lblock 12, the important feature being the offsetmounting arrangement. By mounting the bearings in offset or staggeredrelationship with ,respect to one another, so that each ball bearing ofa pair rotates in a different plane, the wear on the rod is notconcentrated in one spot as would be true if the bearings were directlyopposite one another. The bearings 22, 24 and 32 are preferably standardradial ball bearings having built-in shields or seals to retain theirlubricant and to keep out dirt and dust. Identical bearings may be usedin each instance.

The magnets 26 are of the permanent type and are shimmed forapproximately '1A-2 inch clearance with the rod 30. Magnets may beinstalled between each pair of supporting bearings, or between everyother pair of supporting bearings as shown, FIGURE 1. Other forms ofmagnetic devices including electro-magnets could be employed if desiredto accomplish the same purpose.

For decurling light weight papers having a 50 lb. or less basis weight,the rod 30 would be on the order of 5%; inch diameter for achieving thebest results. For papers 50 to 120 lb. basis weights, 1/2 inch diameterrods are satisfactory. For papers and paperboards over lb. basis weight,5/8 and 34 inch rods have been used successfully. The spacing betweenthe pairs of supporting bearings is not critical. For and 1/2 inch rods,four inch spacings have been found adequate. For inch rod, eight inchspacings have proven satisfactory.

The curl breaker assemblies can be made in any desired length by using amultiplicity of support bearings and magnets, together with a rigidsupporting -bar 10 stiff enough to avoid excessive deflection.

It is contemplated that the apparatus of this invention may be usedsingly, in tandem, or in pairs one reversed from the other (FIGURE 6) inorder to carry out the desired purpose. Generally the apparatus will bepositioned on the machine so that the web can be properly tensioned whenit passes over the decurling rod. The angle of wrap necessary to inducea given amount of curl can be calculated knowing the basis weight of theweb and the size of the decurling rod.

A second embodiment of the novel magnetic curl breaker is illustrated inFIGURES 7-9. During the coursevof the development of the novelarrangement described hereinbefore, at least one prototype rotating rodcurl breaker was tried which consisted of a hardened and ground rod inair lubricated bearings. Standard Oilite bronze bearings with thelubricant removed were used with the top three-fifths of the bearingbeing ground away leaving a cup shape for the bar to rotate in. An airchannel was provided under the bearings and they were clamped in place.The apparatus was then operated by applying compressed air through theair channel and bearings to support the rod. End caps were thennecessary to retain the rod within the cup shaped bearings when the rodwas not in contact with the paper web. i

The apparatus illustrated in FIGURE 7 then became an outgrowth of thepreliminary approach described above. In this instance, air lubricatedbronze bearings 40 have been substituted for the ball bearings used inFIGURES 1-5. The use of these air lubricated bearings 40 in combinationwith the magnets 26 provides an operative structure which is thefunctional equivalent of the previously disclosed apparatus of FIGURES1-5. The rigid support structure remains the same except that it isdrilled with an opening 42 to provide the air supply conduit forlubricating the bearings 40. Each lubricated bearing unit comprises abase member 45 tted in a slot 46 machined in support means 10, and fixedby bolts or the like 47 to the rigid support structure. The base member45 has air conduits 48 drilled therein which are adapted to be alignedwith cooperating air conduits 50 located in the support structure 10.The air conduits 50 are perpendicular to the main supply conduit 42.also located in support structure 10. With this arrangement, compressedair can be supplied through conduit 42 and distributed evenly to theporous bearing 40 via connecting conduits 48, 50. The apparatus is thusseen to provide an air film at the bearing surface 40 on which the rod30 may ride.

Referring now to FIGURE 9, means for retaining the bearing 40 in itsbearing seat is illustrated. In order to accomplish this requirement apair of retaining plates 52 are secured to the base member 45 by screwmeans 54. As can be noted from the drawing, the retaining plates 52 areeach machined so as to t smoothly with the side edges of the base member45 and to cooperate but not interfere with the rotation of the rod 30.Retaining plates 52 do not hold the rod 30 in the bearing seat since themagnetic means 26 located on each end of the bearing unit (FIGURE 7)performs the hold down requirement. This embodiment has been found towork satisfactorily and would prove useful where a supply of compressedair was readily available.

Trials performed with the magnetic curl breaker, using ball bearings asa low friction bearing means, have shown conclusively that mechanicalcurl can be satisfactorily removed from just about any grade of paper.Of course, for light basis weight paper, the smaller the diameter thedecurler rod should be. In addition, for coated papers, it may be deemeddesirable to use a covered rod to further reduce any tendency to producescratches on the paper surface. For that purpose, a plastic coateddecurling rod 60 is illustrated in FIGURE 10. Any suitable smoothplastic 62 may be used without interfering with the holding power of themagnets nor causing an excess amount of friction. FIGURE 11 shows an endview of the plastic covered rod of FIGURE 10 to illustrate the close titthat the plastic 62 assumes around the rod 60.

Another form that the decurling rod may take is illustratcd in FIGUREl2. For this embodiment, a helical spring 64 is shown. In the case wherethe spring 64 is used, it has been found desirable although notnecessary to use a plastic coating over the spring to prevent scratchingof the paper. As a matter of fact, when the magnetic curl breakerassembly of this invention is utilized as a bowed or spreader roll, thehelical spring covered rod 64 may be used to achieve the proper amountof curvature. However, a solid small diameter rod could be used just aswell. As explained hereinbefore, the bowed roll is generally used tominimize cross machine direction shrinkage in the manufacture of paperon the paper machine. The magnetic curl breaker of the present inventionwhen used like a bowed roll as described above, would be employed toreduce the tendency for the paper to wrinkle in an otf machineoperation. A further advantage of the bowed roll magnetic curl breakerwould be the desirable decurling of the paper web in the machinedirection due to roll curl.

A schematic showing of how the magnetic curl breaker of the presentinvention might be used as a bowed roll is illustrated in FIGURES 13 and14. In this embodiment the curl breaker rod could be solid if the bow isvery slight, or the spring type rod 64 as shown in FIGURE 12 wheregreater bow is required. The rod is supported by ball bearing assemblies22, 24 mounted on brackets 12 similar to the arrangement shown in moredetail in FIG- URES 1 5. Located between the ball bearing assemblies arethe usual hold down magnets 26. These magnets and the brackets 12 arefxedly attached to the support means 10 in any suitable manner. For thebowed roll installation, the mounting bracket is shown as beingsupported by adjustable support elements 68 from the base 70. Theadjustable support is necessary to provide the degree of bow at itscenter to accomplish the desired results. FIGURE 14 shows in detail aschematic representation of how the adjustable support 68 could operate.The support consists of a threaded rod 67 screwed into the supportelement 10. The opposite end of the rod 67 is universally mounted in thebase 70 with a ball element 66. Hence, when the adjustable support 68 isturned, the support element 10 including the decurler rod 64 moves up ordown as desired. Of course, any other suitable means could be used tomount the bowed roll as long as it was adjustable. Where a predeterminedfixed bow is satisfactory, a suitably curved support 10` may beemployed.

The foregoing description is deemed to be illustrative of the invention.

I claim:

1. A decurler apparatus for conditioning a tensioned web of paper or thelike comprising;

(a) a rigid support means adapted to extend across the width of the web;

(b) a thrust bearing located at each end of the rigid support means;

(c) a freely rotatable rod of magnetically attractable material mountedbetween said thrust bearings;

(d) a plurality of low friction bearing elements secured to said supportmeans at spaced locations to cradle said rod throughout its length; and,

(e) a plurality of magneticdevices secured to said support means atspaced locations betweenthe low friction lbearing elements in closeproximityy to said rod whereby said rod is retained in place on'the lowfriction bearing elements by magnetic attraction.

2. The apparatus of claim 1 wherein said low friction bearing elementsof paragraph (d) further comprise;

(1) pairs of ball bearings mounted on support blocks so that the ballbearings of each pair rotate in planes which are off-set from oneanother.

3. The apparatus of claim 2 wherein the ball bearings of each pair arefurther mounted on the support blocks with;

(2) their respective axes of rotation spaced aparta distance Which isless than the diameter of one ball bearing so that the ball bearingsoverlap one another and form a shallow V-shaped cradle for said rod.

4. The apparatus of claim 3 wherein the magnetic devices -of paragraph(e) comprise;

(1) permanent magnets which vare xedly secured in a groove located insaid rigid support means.

5. The apparatus of claim 1 wherein said low friction bearing elementsof paragraph (d) further comprise;

(1) air lubricated bearings mounted on a 4bearing block and shaped toprovide a cradle for said rod.

6. The apparatus of claim wherein said air lubricated bearings each;

(2) extend longitudinally of said rod to support the rod throughout itslength and include air conduits which are aligned with cooperatingconduits in said rigid support means whereby lubricating air may besupplied to said bearing surface adjacent said rod.

7. The apparatus of claim 6 wherein said air lubricated bearings eachfurther include;

(3) retaining plates attached to said bearing block to keep the bearingsurface in its seat.

8. The apparatus of claim 1 lwherein the rod of paragraph (c) has aplastic cover.

9. The apparatus of claim 1 wherein the rod of paragraph (c) is formedfrom a helically wound spring.

10. The apparatus of claim 1 wherein said rigid supporting means ofparagraph (a) is further;

(1) adjustably mounted on a base member with a plurality of adjustableelements which extend between the rigid supporting means and the basemember.

11. The apparatus of claim wherein said adjustable elements eachcomprise;

(2) a universal portion in the base member and a threaded portionextending into a cooperating threaded opening in the rigid support meanswhereby 10 support means;

(c) a. freely rotatabl rod of magnetically attractable material mountedbetween the thrust bearings of each rigid support means;

(d) a plurality of low friction bearing elements secured to each rigidsupport means at spaced locations to cradle said rod throughout itslength; and,

(e) av plurality of magnetic devices secured to each rigid support meansat spaced locations between the low friction Vbearing elements in closeproximity to said rod whereby said rod is retained in place on the low,friction bearing elements by magnetic attraction.

13. The apparatus recited in claim 12, wherein the rigid support meansof paragraph (a) are each;

(1) mounted on arrn assemblies which are in turn pivotally attached to amachine frame member.

References Cited UNITED STATES PATENTS 3/ 1904 Ostrandel' 162-27112/1959 Zernov 162-271 X ALLEN N. KNOWLES, Primary Examiner

